Wood grinding machine



Jan. 28, 1936.

A. N. RUSSELL ET AL wooD GRINDING MACHINE Filed May 18, 1932 6 Sheets-Sheet l ATTORNEY jan. 28,1936. A N RUSSELL ET AL 2,029,125

WOOD GRINDING MACHINE Filed May 18, 1932 6 Sheets-Sheet 2 INVENTORS ANDREWNRUSSELL JOHNDROBB ATTORNEY jan. 28, 1936. A N, RUSSELL ET AL 2,029,125

WOOD GRINDING MACHINE Filed May 18, 1932 6 Sheets-Sheet 5 f 1I i0 5 Il HE 65h 63a TNVENTGRS 63. l 68 ANDREWNRUSSELL JOHN .D. RO BB ATIDRN EY Jam 23 3936 A. N. RUSSELL ET AI.

WOOD GRINDING MACHINE Filed May 18, 1932 6 Sheets-Sheet 4 Iml'ml mns ANDREWNRUSSELL J OHNDROBB gg@ ATTORNEY Jan. 28, 1936. A. N. RUSSELL ET Al.

WOOD GRINDING MACHINE Filed May :'8, 1932 6 Sheets-Sheet 5 1N VENTORS ANDR EN NRUSSEL JOHNJILROBB mm/Z ATTORNEY Fam 23 i936- A. N. RussELL'Er AL WOOD GRINDING' MACHINE Filed May 18, 1952 6 Sheets-Sheet 6 I NVE N'IORS ANDREWNRUSSELL JoHNnRoBB BMWZ AT TORNEY Patented Jan. 28, 1936 UNITED 'STATES PATENT OFFICE WOOD GRINDING MACHINE Andrew N. Russell and John D. Robb, Lachine,

Quebec, Canada, National Trust Company Limited, executor of said John D. Robb, deceased, assignors to Dominion Engineering Works Limited, Lachine, Quebec, Canada Application May 18, 1932, Serial No. 612,125 In Great Britain August 11, 1931 8 Claims. (Cl. 83--75) This invention relates to pulp wood grinders reverse movement of said members, the pressure of the continuous feed or magazine type and is applying pawls are automatically retracted from a continuation, in part, of my prior U. S. applicaengagement with the wood charge so that the tion Serial No. 431,908, led February 2'7, 1930, feeding members are permitted to slide freely Patent No. 1,948,189 issued February 20, 1934. past the wood during such return movement. 5

The pocket type of grinder in general use Each feed member is connected to a piston operbefore the advent of the magazine grinder ating in a cylinder equipped With a valve mechaconsisted of a plurality of Wood receiving pocknism controlling the ow of operating fluid in ets equipped with hydraulic pressure plates or such manner that the piston and the feed memfollowers functioning to feed the wood to the ber connected therewith are alternately moved working surface 0f the grinding element. This towards and away from the grindstone. The type of grinder has certain advantages incident valves controlling the various cylinders may be to the direct application of hydraulic or elastic opoperated either manually or automatically in erating fluid, but the disadvantages, such as high order to reverse the movement of the pistons and operating cost with comparatively low output, the feed members connected therewith, but it is led to the development of the magazine grinder. preferred that these ValVeS be Operated in Sliell Magazine grinders are usually equipped with a manner that when one of the feed members endless belts having specially formed links or is moving away from the grindstone, the remainother devices for engaging and feeding the wood ing feed members will all be moving in the oppoto the working surface of the grinding element. site direction, so that the mass of wood contained These chains are operated at a very slow conin the magazine will be continuously subjected to stant speed from either an oil or an electric a substantial and uniform feeding pressure. For motor through the intermediary of a complicated exampley assuming that four feeding members reduction gearing. This arrangement, as comare provided at eaeh Side of the magazine, the pared with the pocket type grinder, provides for flow of fluid to and from the cylinders controlling continuous feeding of the wood to the grinding said feed members will preferably be controlled element and has certain other advantages, such in such manner that when one of the feed memas low labor costs incident to magazine charging bers is moving away from the grindstone the and general operation. The principal disadvanremaining feed members Will be moving in the tage oi the magazine grinder resides in the fact direction of said stone, so that the charge of wood that the chains or other devices employed for is, at all times, subjected to the pressure of seven feeding the wood to the grinding element are of the operating cylinders. As the rate at which operated by a driving mechanism which lacks the the feed members move, during the working elasticity of the direct hydraulic feed employed strokes, iS retarded by the grinding Operation and in the pocket type grinder and it is well recogis considerably slower than the rate at which the nized that, from a grinding standpoint, the best feed members move during the return Strokes, it results are obtained when the wood is pressed to will be seen that the period 0f time When the grinding surface by the direct application of only seven of the eight cylinders are applying fluid pressure. pressure to the wood will be comparatively short The purpose of the present invention is to proand that, during the greater part 0f the grinding 40 vide an improved type of magazine grinder in operation, the wood is subjected to the preSSllre which the wood is continuously fed to the workof all of said Cylinders. When it is desired to ing surface of the grinding element by the direct remove the load from the erndstone, the feedapplication of uid pressure, ing members may be employed as lifting devices According to this invention, the wood charge for lifting the Wood Charge aWay from the WOIkplaced in the magazine is Continuougy fed to ing surface of the stone. In order to accomplish the working surface of a rotary grindstone by this, suitable means are provided for securing means 0f two groups of reciprocabie feed memthe pawls of certain feed members against pivotal bers arranged at opposite sides of the magazine movement So that, during the return Stroke 0f and actuated by the direct application of fluid Said members the paWlS Will apply pressure to pressure. These feed members are each provided mOVe the Wood Charge in a direction aWaB7 from with a plurality of pivotally mounted pawls northe Working Surface or the Stone. mally arranged to apply feeding pressure to the Proceeding now to a more detailed description wood charge only during movement of the memof this invention, reference will be had to the bers in the direction of the grindstone. During accompanying drawings, in which,

Figure 1 isa vertical sectional view through the grinder in a plane at right angles to the axis of the grindstone.

Figure 2 is a View partly in Vertical section and partly in side elevation in a plane parallel with the axis of the grindstone.

Figure 3 is a transverse sectional view along the line 3-3 of Fig. 2.

Figure 4 is a transverse sectional view along the line 4 4 of Fig. 1.

Figure 5 is a transverse sectional view Valong the line 5-5 of Fig. 1.

Figure 6 is a transverse sectional view of a timing valve mechanism. Y

Figure 7 is a View partly in side elevation and partly in longitudinal section of the timing Valve mechanism appearing in Fig. 6.

Figure 8 is a vertical sectional View through a duplex valve mechanism controlling the flow of fluid to and from opposite sides of the power piston associated with each feed member.

Figure 9 is a vertical sectional View taken along the line 9-9 of Fig. 8. In this'view a portion of the power piston and cylinder controlling the operation of one of the feed members also appears in vertical section.

Figure 10 is a View similar to Fig. 9 but taken along the line lll-' l of Fig. 8.

FigureY 11 is a transverse sectional view taken along the line of Fig. 8.

Figures l2 and 13 are diagrammatic views illustrating the action of the duplex valve mechanism appearing in Figs. 8 to ll inclusive.

Figures 14, 15, 16 and 17 are enlarged detail Views'ofV the drive connection provided between each feed member and the timing shaft controlling the operation of the timing valves appearing in Figs. 6 and 7.

Figure 18 is a transverse sectional view through one of the pawls carried by the reciprocable feed members.

Referring more particularly to the drawings, designates Va rotary grindstone carried by a shaft l2 (see Figs. l and 5) journalled in suitable bearings I3. Casings M, mounted'at opposite sides of the grindstone, carry vertically moveable screws I5 adapted to be raised and lowered by, the encased worm or other gearing generally 'indicated at I6. The lower ends of screws |5 are fixed to a casting I1 forming the lower'end of themagazine IB. The casting Ill is of well known construction and is adapted to have its lower face maintained in proper relation tothe working surface of the grindstone by suitable adjustment of the screws |5. Y

The magazine structure includes a series of flanged beams I9 arranged at opposite sides of the magazine and spaced'apart, as shown inY Figures 3 and 5, to provide a series of Vertical Y guidewaysZ. Mounted in each guideway isa reciprocable feed member comprising side plates 2| having their upper ends joined together by a cross member 22. Each feed member carries a series of vertically spaced pawls 23 mounted between the side plates'Zi on suitable pivots 24. The pawls are normally balanced on the pivots so that the heel portions 25 rest on cross bars 25 connecting the side plates 2| while the toe portions 21 project beyond the side plates into the wood receiving space of the magazine. Each feed member is connected to the lower end of a piston rod 28 b'y a pin 29 passing through suitable lugs 3B carried by the upperV cross member 22. The upper end of each piston rod 28 is connected to a power piston 3| operating in a power cylinder 32. Each power cylinder is equipped Y as hereinafter described with suitable valve mechanism for controlling the flow of operating fluid to and from opposite sides of the power piston 3|.

From the foregoing description it will be evident that the feed members, operating in the guideways 20, are raised and lowered as the operating uid is alternately admitted into the upper and lower ends of the power cylinders 32 The z to raise and lower the power pistons 3|. side plates 2| of the feed members are arranged to travel inthe guideways free of contact with the wood charge and are preferably equipped with rollers 33 travelling on suitable tracks 34 carried by the beams I9. movement of the feed members the pawls 23 assume a position with their projecting toey portions 21 engaging the wood charge 35 and their heel portions resting on the crossbars 26 so that pressure is applied through thev pawls to',

force the wood charge in the direction of the grindstone. It Will be noted here that the pawls are .provided with longitudinally curved lower edges 35 for'engagement with the wood charge.

This curvature is predetermined so that the pressure of the pawls is applied to the wood charge in a direction at such an angle to the direction of movement of the .feed members that the applied pressure is properly distributed throughout the entire mass of the wood charge. of the pawls are also formed with a slight transverse curvature as shown to advantage in Figure |8. This transverse curvature is such as to During downward The edges 36 L..

eliminate sharp corners at the sides of the pawls which would tend to shear orV break the fibres ofthe wood. During upward movement of the feed members the toe portions of the pawls swing downwardly about the pivots 24 and out of en- Y ing feed members are on their downward or i.,

working strokes.V With this method of control the wood charge is at all times subjected to the pressure of at least seven of the feed members. Moreover, since the return stroke of Veach feed member is completed 1n a Vfraction of the time required to complete the working stroke, the pressureof the eight feed members is simultaneously applied to the wood charge during of the time the grinder is in operation.

As herein illustrated the control mechanism for the power pistons 3| is designed to provide a working stroke at slow speed with considerable power and a rapid return stroke with comparatively little power. To this end each power cylinder 32` is equipped with low and high pressure valves; the low pressure valve controlling the flow of low pressure uid to and from the lower end of the cylinder and the high pressure Valve controlling the flow of high pressure nuid to and from the upper end of the cylinder. These valves are shown in detail in Figs. 8 to 11 inclusive and the action thereof is diagrammatically illustrated in Figs.'12 and 13.

As shown to advantage in Fig. 8, the low pressure valve 38 and the high pressure Valve 39 operate in suitable valve sleeves 48 and 4I and have their intermediate portions reduced in diameter to provide the annular grooves indicated at 42 and 43. The valve sleeves are arranged in parallel cylinders 44 and 45 formed in a single casting 48 attached to one of the power cylinders 32.

The low pressure valve cylinder 44 is provided with three annular passages 4l, 48 and 49. These passages are separate from one another and communicate with the interior of the valve sleeve 48 through suitable openings 50. Passage 41 also communicates with the low pressure inlet 5I to which uid at comparatively low pressure (8O to 100 lbs. per sq. in.) is supplied from any suitable source. Passage 48 communicates with a port 52 leading to the lower end of cylinder 32. Passage 49 communicates with a port 53 (see Fig. 11) leading to an exhaust connection 54.

The high pressure valve cylinder is also provided with three separate annular passages 56, 5l and 58 communicating with the interior of the valve sleeve 4i through openings 59. The lower passage 55 communicates with the high pressure inlet 8i! to which fluid at comparatively high pressure (200 to 300 lbs. per sq. in.) is supplied from a siutable source. The intermediate passage 5l communicates with a port 5l leading to the upper end of power cylinder 32. The upper passage 58 communicates with the previously mentioned port 53 leading to the common discharge connection 54.

The valves 38 and 38 are actuated in unison by a diiferential piston 63 to which the valves are connected by the valve stems 38a and 39a; yoke 53a, and piston rod 53h. Piston 53 operates in a differential cylinder 64 and its lower end is continuously subjected to water pressure supplied to the lower end of cylinder 84 through a branch 55 of the water supply main 88. Provision is also made for supplying water pressure to the upper end of cylinder 84 through a branch 81 of the supply main 68 or through a further supply main 58. The ow of water into cylinder 84 through the branch 6l is controlled by a manually operable three way valve 89. This valve is only used occasionally and is normally positioned to close oif the flow through the branch 8'? without interfering with the flow through the main 58. The flow through the main 88 is controlled by an automatic timing valve mechanism which, as hereinafter described, functions to alternately connect the main 68 with a source of water pressure and with a drain pipe.

For the downward or power stroke of the power piston 3l the valves 38 and 39 and the differential piston 63 are positioned as indicated in Figs. 8 to 12 inclusive. In this position the high pressure valve 39 permits the high pressure fluid to flow into the upper end of cylinder 32 via the high pressure inlet 88, passage 56, valve sleeve 4I, passage 51 and cylinder port 8|. At the same time valve 38 permits the low pressure fluid, previously supplied to the lower end of cylinder 32, to escape, via cylinder port 52, passage 48, valve sleeve 48, passage 48, and exhaust port 53, to the common exhaust connection 5.

For the return stroke of the power piston the valves 38 and 39 and the differential piston 83 are positioned as shown in Figure 13. In this position valve 38 permits low pressure uid to flow into the lower end of cylinder 32 via low pressure inlet 5|, passage 4l, valve sleeve 4l, passage 48 and cylinder port 52. At the same time valve 39 permits the high pressure fluid, previously supplied to the upper end of cylinder 32, to escape, via cylinder port 8l, passage 5l, valve sleeve 4l, passage 58 and exhaust port 53, to the common exhaust connection 54. The high and low pressure fluid alternately escaping through the eX- haust connection 54 is conducted to a suitable sump or storage tank (not shown).

As previously stated the valve 69 is normally positioned to close the delivery end of the branch 61 the water main 53. During the working stroke of the power piston 3l the valves 38 and 39 and the differential piston 83 are held in the position shown in Figs. 8 to 12 inclusive by the pressure of the water entering the lower end of cylinder 84 via the branch 85 and acting against the lower end of piston 63. At this time the main 88 is connected to drain through the timing valve mechanism and functions as a discharge pipe for the water pressure previously admitted to the upper end oi cylinder 54. For the return stroke of the power piston 3! the timing valve mechanism operates to connect the main 68 with a source of water supply so that water under pressure flows through the main 88 into the upper end of the cylinder 54 where it acts on the upper surface of the piston 63 and serves to shift said piston and the valves 38 and 39 to the position shown in Fig. 13. As the differential piston S3 is shifted to the last mentioned position the water previously supplied to the lower end of cylinder 54 is forced back into the branch 85.

In the normal operation of the grinder the shifting of the various valves 38 and 39 from the position shown in Fig. 12 to that shown in Fig. 13, and vice versa, is repeated indenitely under the control of the valve timing mechanism governing the operation of the differential pistons 63. The manually operable control valve 59, associated with each diiferential piston E3, is usually operated only when the feed member controlled by said piston is to be actuated out of its proper sequence. The necessity for this arises, for example, when one of the feed members becomes jammed before completing its working stroke. In such an emergency the feed member may be immediately returned to its starting point by turning the valve 89 to a position closing the main E8 and placing the upper end of the cylinder 84 in communication with the branch connection 8l. When the valve 89 is returned to its normal position this feed member immediately resumes its proper place in the normal operating sequence of the feed members as determined by the timing valve mechanism.

The timing valve mechanism controlling the diiferential pistons 63 is shown in Figs. l to 7 inclusive and also appears, in detail, in Figs. 14 to 17 inclusive. The purpose of this timing mechanism is to govern the operation and reversal of the power pistons 3! to maintain the proper sequence of motion among the several feed members throughout the operation of the grinder. To this end each feed member carries a bracket ll having an opening 'l2 loosely receiving a threaded rod 'i3 therethrough. The feed member and the rod 13 are capable of relative movement within the limits set by a pair of stop nuts 14 and 'l5 carried by the rod and positioned above and below the bracket ll. At its upper end the rod 'i3 carries a rack i6 which slides vertically in a guide shoe il, against one side of which the rack is held by a spring I8 with suicient pressure to prevent the rack and rod falling by their own weight. During the working without interfering with the flow through strolse of the' feed member the rod i3 and rack 'i6 are forced downwardlly by engagement of the bracket lli with the lower stop nut '55.. On the upward stroke of the feed member the rod 'i3 and rack 'l are lifted by engagement of the bracket li with the upper stop nut it. When the feed member is atthe top of its upward stroke the clearance between the bracket 7l and the lower nut 'I5 permits the feed member to move downwardly a limited distance at the start of the power strokebefore exerting a downward pull on the rod it. This takes care of any slip which may occur at the start of the downward stroke of the feed member before the pawls engage the wood charge and prevents the control Vmechanism, which is actuated by the racks it,

being adversely affected by such slippage.

Each rack i6 meshes with a gear 'i9 carried by a shaft ii on which the gear is free to turn. Gear i9 carries a plurality of pivoted pawls 9i engaging a ratchet wheel 82 keyed to the shaft 89.

As shown to advantage in Figs. 14 and i7 each gear 'E9 is made in two parts 'i9a and 7Gb held together by bolts 9S. on certain of the bolts 93 and are held to the ratchet by suitably arranged springs 84. VAs shown more particularly in Figs. l and 5 there j are two shafts 323 arranged at opposite sides of the magazine in suitable bearings 85 and each shaft carries four gears 'i9 meshing with the racks i9 driven by the adjacent group of feed members. During the upstroke of the racks 'i9 the pawls 9i slip freely over the ratohets S2 and permit the gears i9 to turn freely on the shafts 89 without imparting motion thereto. During the downstroke of the racks the rack of each group which happens to be descending at the greatest rate of speed serves to drive its associated shaft Si? through the medium of the engaging drive gear '19. Y

The shafts 913 are provided with bevelled pinions 8l in driving engagement with similar pino-ns 9S fixed to the ends of a valve timing shaft 88 journall'ed in suitable bearings 9d. The shaft 89 carries the valve operating cams 9i which are equal in number to the number of feed members operating in the magazine I8. In the present instance there are eight cams arranged in two groups of four each located at opposite ends of the shaft 99. The relative angular displacement of the cams is such that the cam lifts 9! are equally spaced radially of the shaft 39 so that the sumof the spaces equals one revolution. In other words the shaft 89 and the cams Y 99 make a complete revolution in the time reupper portion partitioned olf to provide fourV separate transverse chambers 93, each chamber being located directly below one of the cams 90. Below the transverse chambers 93 the valve boxY is partitioned ofi to provide two separate longitudinal chambers Stand 95, the chamber 9d being connected to a water supply pipe 96 and the chamber 95 being connected to a drain pipe 97. Each chamber 93 is equipped with a pair of valves including inlet valve 98 opening into the supply chamber 99 and an outlet valve 99 opening into the drain chamber 95. The valves 93 and 99 normally tend to close under the inuence of the springs E99 and I9! encircling the valve stems E92 and |93 and acting against the abutments ii and H35 at the upper ends of the valve stems. Mounted directly above each pair The pawls 8i are mounted Si, the several rockers being properly positioned 3.1-

on the shaft H99 suitable spacers H2.

Each transverse chamber 93 is connected to the upper end of one of the diiferential cylinders 95 by one of the previously mentioned mains Se.

When the valves 99 and 99, controlling said chamber, are in the position .shown in Fig. 3 it will be evident that the upper endof the cylinder 961 is connected to the drain pipe 9i. Consequently the pressure supplied to the lower end of said cylinder 5ft is effective to shift the differn ential piston S3 and the associated power cylinder control valves 38 and 39 to the position shown in Fig. 8 so that the piston operating in the power cylinder is forced downwardly on its working Stroke. At each complete revolution of the shaft e S9 the Valve 99 Vis closed and the valve 98 opened by movement of the controlling rocker 96 in response to engagement of the cam lift 9| with the set screw iii. During the brief period that the'valves 99 and 99 arein the last mentioned fr position the main 99 is Vconnected tothe supply serves Yas, a pressure supply main for the upper end of cylinder 353 with the result that the differential piston and the power cylinder control valves 38 and 39 are positioned as shown in Figure 13 so that the power piston is returned to its starting position. When the cam lift 9| passes out of engagement with the set screw lil the timing valves 98 and 99 are immediately returned to the position shown inV Fig. 6, since the pressure exerted against the rocker 06 by the valve spring I Eil is greater than Vthat exerted by the spring |93.

The foregoing description of the timing valve f mechanism applies with respect to the operation of each pair of timing valves 98 and 99 and it will be understood that the operatingrsequence of the power piston and feed member controlled by each pair of timing valves is determined by the angular displacement of the associated operating cam 90, the several cams being so arranged on the shaft 89 that when one of the eight feed members is on its upward stroke the remaining feed members are all descending and applyt.;

ing pressure to the wood charge.

A particular advantage of the valve timing mechanism herein described is that the feed members are automaticaily moved upwardly on the return stroke at predetermined intervals of .1.'

time, regardless of whether or not the said feed members have completed or only partially completed their pressure applying strokes. The merit of this arrangement resides in the fact that when one of the feed members becomes jammed during the working stroke it will remain inactive only during the interval of time required for the timing valve mechanismto reverse the ow of uid to the power cylinder connected with the feed member. As soon as this occurs the feed member is quickly raised to the end of its return or non-working stroke and then begins to move downwardly on the working stroke. It will also be evident that, since the feed members move freely past the. Wood charge during the return or non- Vpipe 955 through the chambersf93V and S4 and Y working strokes, these members will not become permanently jammed by arching or bridging of the wood within the magazine. When such arching or bridging does occur the pressure applying strokes of the feed members will, of course, be retarded or arrested but, at predetermined intervals controlled by the timing valves, each feed member will move freely on its return stroke and will then immediately move in the reverse direction to apply pressure to the wood charge at a somewhat different point. In other words whenever there is arching or bridging of the wood within the magazine the limited reciprocating movement which the feed members are permitted to have results in the pawls 2 constantly changing their positions to apply pressure to different portions of the wood charge until the arch or bridge is broken down.

When it is desired to remove all load from the grindstone l i, certain of the feed members may be employed as lifting devices for moving the wood charge away from the working surface of the stone. To this end the heel portions of two opposing feed members are temporarily secured to the cross bars 26 by clamps il@ held in place by suitable screws lll. The pawls are thus tied down to maintain a horizontal position during upward movement of the feed members. The feed members employed as lifting devices are preferably operated manually by actuation of the valves 69.

Referring again to the power cylinder control valves 38 and 39 it will be noted that, in all positions of the valves, the grooves 42 and 43 are in communication with the pressure inlets 5! and Si@ and that the upper and lower ends of the valve cylinders 44 and 45 are open to the exhaust port. The advantage of this arrangement is that the Valve mechanism is relieved of all loads due to pressure. and any leakage occurring is free to drain away through the exhaust. Adjustment of these valves is provided for through the medium of suitable thimbles IIA which are threaded on the valve stems 38a and 39a and secured to the yoke 63a by lock nuts I I5. Any slight misalignment of the valves is compensated by loose tting of the thimbles in the receiving openings of the yoke.`

Having thus described our invention, what we claim isz- 1. A pulp wood grinder comprising a magazine, a plurality of reciprocable feed members arranged therein, a piston connected to each feed member, a separate cylinder for each of said pistons, high and low pressure uid supply lines, a valve mechanism for each cylinder operable to periodically connect one end of. said cylinder with the high pressure fluid supply line to effect a working stroke of the feed member and to periodically connect the remaining end of the cylinder with the low pressure fluid supply line to effect a return stroke of the feed member, said valve mechanism also serving to connect each end of the cylinder with an exhaust line during admission of iluid to the opposite end of the cylinder, a differential piston connected to operate said mechanism to positions alternately connecting each end of the cylinder with its respective fluid supply line, a differential cylinder containing said differential piston, one end of said differential cylinder being in constant communication with a pressure line, and means functioning periodically to alternately connect the remaining end of the differential cylinder with a pressure line and with an exhaust line.

2. A pulp wood grinder comprising a magazine, a plurality of reciprocable feed members arranged therein, a piston connected to each feed member, a separate cylinder for each of said pistons, high and low pressure fluid supply lines, a valve mechanism for each cylinder operable to a position connecting one end of the cylinder with the high pressure fluid supply line or to a position connecting the remaining end of the cylinder with the low pressure fluid supply line, said valve mechanism also serving to connect each end of the cylinder to an exhaust line when positioned to connect the opposite end of the cylinder with its respective fluid supply line, a differential piston connected to operate said valve mechanism, a differential cylinder containing said differential piston, a fluid supply line connected to one end of the differential cylinder so as to be in continuous communication therewith, a valve mechanism functioning to alternately connect the re- '1 maining end of the differential cylinder with a pressure line and an exhaust line and means actuated by the feed members for controlling said last mentioned valve mechanism.

3. A pulp wood grinder comprising a magazine, a plurality of reciprocable feed members arranged therein, a piston connected to each feed member, a separate cylinder for each of said pistons, a valve mechanism associated with each cylinder to control the flow of fluid to and from opposite ends of the cylinder, racks movable in opposite directions in response to corresponding movement of the feed members, pinions meshing with said racks and means actuated by rotation of the pinions during the working strokes of the t).

feed members for operating the valve mechanisms of the different cylinders in a definite sequence.

4. A pulp wood grinder comprising a magazine, a plurality of reciprocable feed members arranged therein, a piston connected to each feed member, a separate cylinder for each of said pistons, a valve mechanism associated with each cylinder to control the flow of fluid to and from opposite ends of the cylinder, a rack slidably mounted in proximity to each feed member, means on each feed member adapted to move the rack in one direction or the other depending upon the direction of movement of the feed member, a pinion meshing with and adapted to be rotated by each rack, a timing shaft, drive connections between the pinions and timing shaft including pawl and ratchet devices functioning to drive the timing shaft only during the working strokes of the feed members and means controlled by rotation of the timing shaft for operating the valve mechanisms of the different cylinders in a definite sequence.

5. A pulp wood grinder comprising a magazine, a plurality of reciprocable feed members arranged therein, a piston connected to each feed member, a separate cylinder for each of said pistons, a valve mechanism associated with each cylinder to control the flow of motive fluid to and from opposite ends of the cylinder, a timing shaft, means controlled by rotation of the timing shaft for operating the valve mechanisms of the different cylinders in a definite sequence, and means actuated by the feed members for rotating the timing shaft only during the working strokes of said feed members, said last mentioned means comprising drive shafts geared to the timing shaft, pinions rotatably mounted on each of said drive shafts, a rack movable with each feed member and meshing with one of said pinions, said pinions being provided with pawls engaging CII ratchets on their respective drive shafts so that said drive shafts are rotated in response to rotation of said pinions only when the feed members are moving on their working strokes.

6. A'pulp wood grinder comprising a magazine, a plurality of reciprocable feed members arranged therein, a piston connected to each feed member, a separate cylinder for each of said pistons, a valve mechanism associated with each cylinder and controlling flow of motive uid to and from opposite ends of the cylinder, an auX- iliary pressure responsive device connected with each valve mechanism for operating the same, valves for controlling the iiow of uid to and from said auxiliary pressure responsive devices, a timing shaft, means actuated by said timing shaft for operating said last mentioned valves in predetermined sequence and means controlled by the movement of the feed members for actuating said timing shaft, said last mentioned means including racks movable with the feed members, pinions meshing with said racks and drive connections between the pinions and the timing shaft including pawl and ratchet devices arranged so that the timing shaft is driven by the feed members only during the working strokes of the said members.

7. A pulp wood grinder comprising a magazine, a plurality of reciproca-ble feed members arranged therein, a piston connected to each feed member, a Separate cylinder for each piston, a valve mechanism associated with each cylinder to control the flow of motive fluid to and from opposite ends of the cylinder, an auxiliary pressure responsive device associated with each valve mechanism for operating the same, means for controlling the operation of said auxiliary pressure responsive devices comprising a series of chambers .each connected with one of said auxiliary pressure responsive devices, valves associated with each chamber and operable to a position connecting said chamber with 4a pressure line or with an exhaust line, a timing shaft, means actuated by rotation of said timing shaft for operating the valves of each chamber in a predetermined sequence with respect to each other and with respect to the valves of the companion chambers, and means actuated by the feed members for rotating the timing shaft only during the working strokes of said members.

8. A pulp Wood grinder comprising a magazine, reciprocable feed members arranged therein, a piston connected to each feed member, a separate cylinder for each of said pistons, a valve mechanism associated with `each cylinder and controlling the flow of motive fluid to and from opposite ends of the cylinder, an auxiliary uid actuated pressure responsive device controlling the-operation of each valve mechanism, a series of chambers, a conduit connecting each chamber with one of said pressure responsive devices,'com mon pressure and exhaust chambers adapted to be alternately placed in communication with each of Y said rst mentioned chambers, a valve controlling communication between said pressure chamber and each of said first mentioned chambers, a second valve controlling communication between said exhaust chamber and each of said first mentioned chambers, a timing shaft, means actuated by said timing shaft for operating thel valves associated with each of the rst mentioned chambers in a predetermined sequence, and means actuated by the feed members for operating the said timing shaft during the working strokes of the feed members.

ANDREW N. RUSSELL JOHN D. ROBB. 

